Electrophotosensitive copiers include a photoconductor with a photoconductive layer with a conductive backing. The photoconductor is transported along an endless path relative to a plurality of work stations, each of which is operative when actuated to perform a work operation on the electrophotosensitive medium. Such stations include a charging station at which a uniform charge is placed on the photoconductive layer, an exposure station at which the charged photoconductive layer is image-wise exposed to actinic radiation from the medium to create an electrostatic image of the medium in the photoconductive layer, a developing station at which the electrostatic image is contacted with finely divided charged toner particles for adhering to the photoconductive layer in a configuration defined by the electrostatic image, a transfer station at which such toner particles are transferred in the image configuration to a receiving surface, and a cleaning station at which residual toner is removed from the photoconductive layer so that it can be reused. The electrostatically held toner image is then adhered to the receiver sheets by flowing the toner particles together.
In seeking high quality images, there are a number of problems which are all related to moisture content of the receiver varying either from sheet to sheet of from side to side in a duplex process. Problems relating to the receiver moisture content from sheet to sheet are toner laydown consistency as receiver charging ability varies with moisture content. Receiver sheet blistering may also occur should some receiver sheets exceed a certain moisture level (critical level is dependent on receiver sheets weight, thickness, clay content, coating, fusing temperature and process speed) from moisture leaving the receiver sheets too quickly. Fusing the toner to the receiver through transportation through a heated nip will dry receiver sheets as well causing it to shrink and then grow again as it regains moisture causing one of the largest problems, front to back registration errors, which are cause by the receiver sheets being smaller when the duplex image is placed on the receiver. To reduce all of these problems the receiver must be preconditioned to reduce the difference in charging ability of the receiver that enters for toner transfer, to gently reduce the moisture content to reduce blistering and to shrink the receiver for the simplex pass to reduce shrinkage through the duplex path. Receiver sheets are preconditioned by passing the receiver sheets through heated preconditioning rotatable rollers which are easy to clean (to remove paper dust), thermally conductive, and exhibiting toner release properties similar to but not as stringent as fuser roller as toned images would rarely come in contact with these preconditioning rotatable rollers.